Add obsx library

metrics.go

@@ -0,0 +1,78 @@
+package obsx
+
+import (
+	"net/http"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+// MetricsConfig configures the metrics factory.
+type MetricsConfig struct {
+	Namespace string
+	Subsystem string
+}
+
+// Metrics is a factory for creating Prometheus metrics with consistent naming.
+type Metrics struct {
+	cfg      MetricsConfig
+	registry *prometheus.Registry
+}
+
+// NewMetrics creates a new Metrics factory.
+func NewMetrics(cfg MetricsConfig) *Metrics {
+	reg := prometheus.NewRegistry()
+	reg.MustRegister(prometheus.NewProcessCollector(prometheus.ProcessCollectorOpts{}))
+	reg.MustRegister(prometheus.NewGoCollector())
+	return &Metrics{cfg: cfg, registry: reg}
+}
+
+// Counter creates and registers a new CounterVec.
+func (m *Metrics) Counter(name, help string, labels ...string) *prometheus.CounterVec {
+	c := prometheus.NewCounterVec(prometheus.CounterOpts{
+		Namespace: m.cfg.Namespace,
+		Subsystem: m.cfg.Subsystem,
+		Name:      name,
+		Help:      help,
+	}, labels)
+	m.registry.MustRegister(c)
+	return c
+}
+
+// Histogram creates and registers a new HistogramVec.
+func (m *Metrics) Histogram(name, help string, buckets []float64, labels ...string) *prometheus.HistogramVec {
+	if buckets == nil {
+		buckets = prometheus.DefBuckets
+	}
+	h := prometheus.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: m.cfg.Namespace,
+		Subsystem: m.cfg.Subsystem,
+		Name:      name,
+		Help:      help,
+		Buckets:   buckets,
+	}, labels)
+	m.registry.MustRegister(h)
+	return h
+}
+
+// Gauge creates and registers a new GaugeVec.
+func (m *Metrics) Gauge(name, help string, labels ...string) *prometheus.GaugeVec {
+	g := prometheus.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace: m.cfg.Namespace,
+		Subsystem: m.cfg.Subsystem,
+		Name:      name,
+		Help:      help,
+	}, labels)
+	m.registry.MustRegister(g)
+	return g
+}
+
+// Handler returns an http.Handler for the /metrics endpoint.
+func (m *Metrics) Handler() http.Handler {
+	return promhttp.HandlerFor(m.registry, promhttp.HandlerOpts{})
+}
+
+// Registry returns the underlying Prometheus registry.
+func (m *Metrics) Registry() *prometheus.Registry {
+	return m.registry
+}